I found the new IFileOperation API to be rather broken.
IFileOperation::CopyFile will abort on the first src not found. -windows 7 x64 sp1
Windows 10 it will attempt to rename the file twice. -try renaming C:\program files\asd3 => C:\program files\asd4 -we get an admin request, the rename happens, and then we fail because we try a second time and C:\program files\asd3 no longer exists. adding a sink does not help.
I too can confirm that the new API does not solve the 80070057 issue on Windows 10 x64 1809.